A conventional electric braking device for a vehicle including an “electric motor generating power”, a “pressing member (brake piston) pressing a friction member (pad) against a rotating member (brake disk) integrally rotating together with a wheel of a vehicle”, a “power transmitting mechanism transmitting the power generated by the electric motor to the pressing member to generate pressing force of the pressing member with respect to the friction member”, and a lock mechanism (parking brake mechanism) is known (for example, see Patent Literature 1).
The lock mechanism mentioned here is a mechanism which includes an “engaged part (ratchet gear) integrally moving together with a power transmitting member included in a power transmitting mechanism” and an “engaging member (claw member) selectively moving to an engagement possible position where the engaging member can be engaged with the engaged part and an engagement impossible position where the engaging member cannot be engaged with the engaged part” and achieves a “locked state” (the engaging member is engaged with the engaged part to make the power transmitting member impossible to move in a reducing direction of pressing force). This “locked state” is achieved to achieve the parking brake function.
In the device described in the above literature, when the “locked state” is achieved in a state in which a pressing member presses a friction member, the engaging member is moved from the engagement impossible position to the engagement possible position, and “supplied power amount reduction control” reducing a power supply amount for an electric motor is performed in a state in which the engaging member is kept at the engagement possible position to move the power transmitting member in the reducing direction of the pressing force so as to engage the engaging member with the engaged part.
The literature does not describe a reduction gradient of a power supply amount when “supplied power amount reduction control” is performed (therefore, a movement speed of the power transmitting member in the reducing direction of pressing force) at all.
When the reduction gradient of the power supply amount (therefore, a movement speed of the power transmitting member) is high, a relative movement speed between the engaging member and the engaged part becomes high. Thus, while a time from “start of the supplied power amount reduction control” to “engagement between both the parts” can be shortened, a relatively large impact load is easily generated on both the engaged parts at the moment of the engagement. In contrast to this, when the reduction gradient of the power supply amount (therefore, a movement speed of the power transmitting member) is low, a relative movement speed between the engaging member and the engaged part becomes low. Thus, while a relatively large impact load is hard to be generated on both the engaged parts at the moment of the engagement, a time from “start of the supplied power amount reduction control” to “engagement between both the parts” becomes long.